...
Get person_id
from user_id
and applicant_person_id
from applicant_user_id
Check relationship using /wiki/spaces/PCAB/pages/17415995422 Relationship between Confidant Patient and Related Patient validation algorithm and having person_id and applicant_person_id
...
Generate new
access_token
according to the logic, described here /wiki/spaces/PCAB/pages/17452269702 RC Exchange oAuth Code Grant to Access Token